Given the same amount of water, subsurface drip irrigation covers a 46% larger wetted volume of soil than a surface drip system.

This decreases the saturation point of the soil, which not only leaves room for more air, but also improves the capillary movement of water and decreases the water lost to deep percolation.

Water distribution 10 hours after 1 hour of watering.
Surface Dripline	Sub-surface drip line